[Relax][Frontend][TFLite] Add BITCAST operator mapping

[as4230]

This PR adds TFLite frontend support for the BITCAST operator which reinterprets a tensor's bytes as a different dtype without converting the underlying data.

The handler lowers BITCAST to relax.op.memory.view which aliases the input buffer with the new shape and dtype.

Frontend tests cover same-width (float32 -> int32, uint8 -> int8), width-changing smaller (int32[3] -> int16[3, 2]), and width-changing larger (int16[5, 2] -> int32[5]).

python -m pytest tests/python/relax/test_frontend_tflite.py -k bitcast -v

Addresses the BITCAST item under #19412.

[gemini-code-assist]

Code Review

This pull request adds support for the BITCAST operator in the TFLite frontend, mapping it to relax.op.memory.view. The implementation includes validation for input/output tensor counts and ensures total byte sizes match, with comprehensive tests added for various data type and shape transformations. Feedback recommends using the to_int_list utility for shape conversion to maintain consistency with the existing codebase and prevent potential type mismatches.

[as4230]

@tlopex - Quick design check. Issue #19412 lists BITCAST and mentions needing a dedicated op. I went with relax.op.memory.view since it's byte-preserving and zero-conversion which seems to match TFLite BITCAST.

If you'd prefer a first-class relax.bitcast op that legalizes to memory.view or if there's a semantic gap with memory.view I'm not seeing I'm happy to implement whatever's missing.

[tlopex]

LGTM! No worries, your implementation is right @as4230